1. Technical Field
The present disclosure relates to a biological graft, especially to a nerve graft.
2. Description of Related Art
A nervous system is a complex cellular communication network that is mainly composed of neurons and glial cells (neuroglial cells). Glial cells occupy spaces between neurons and modulate neurons' functions. The neuron sense features of both external and internal environments and transmit this information to the brain for processing and storage. For example, the neurons receive the diverse types of stimuli from the environment (e.g. light, touch, sound) and convert into electric signals, which are then converted into chemical signals to be passed on to other cells.
Neurons exist in a number of different shapes and sizes, and can be classified by their morphology and function. The basic morphology of a neuron includes a cell body and neurites projecting/branching from the cell body towards other neurons. The neurites also can be defined into two types by their functions. One is a dendrite, which branches around the cell body and receive signals from other neurons to cell body. The other is an axon, which branches from the cell body and grows continually without tapering. The axon conducts the signals away from the neuron's cell body. The end of the axon has branching terminals that release neurotransmitter substances acting as chemical signals into a gap between the branching terminals and the dendrites of other neurons. Thus, the information or signal is propagated.
Once injury to the nervous system occurs, neuron damage will lead to neurite degeneration and retraction. If the damage is severe, breaks in neurites of the neuron are presented. Consequentially, the signal transmission will be affected and the cellular communication with specific neurons will cease. Generally, damage on the neurites will reverse by introducing nerve pipes including degradable biological material to the nervous system to reconnect with the opposite terminals in broken neurites. The neurites grow along the nerve pipes until the neurites are combined together. Thus, the neuron damage is reversed.
However, if a distance between the broken neurites is long, a growing time of the neurites can be long, thus a long recovery time for reversing the neuron damage is required.
What is needed, therefore, is to provide a nerve graft, to overcome the above-described shortcomings.